A solenoid actuator generally has a cylinder portion including a tube made from a magnetic material and a ring of nonmagnetic material disposed along the length of the tube. Performance characteristics, including the force and the stroke of the solenoid, for example, are affected by the design of the magnetic portion and the non-magnetic ring of the tube. The shape, width, and thickness of the nonmagnetic ring can help define the solenoid force and stroke characteristics, for example.
One method of making a solenoid actuator involves depositing a bronze alloy into a groove on a solenoid tube blank and bonding the materials together via tungsten inert gas (TIG) welding. The solenoid tube assembly is then machined to the designed dimensions. This process generally allows a manufacturer to produce a solenoid actuator with the intended force and stroke characteristics; however, significant problems with this process exist.
Solenoid actuators are exposed to internal pressures. The materials used to form solenoid tube blanks, usually steel, and the materials used to form the nonmagnetic ring, usually a bronze alloy, can have different moduli of elasticity. This causes the two materials to behave differently when exposed to internal pressure and often causes high stress areas where the two materials bond, thereby increasing the risk of failure when exposed to internal pressure.
Using TIG welding to bond the ring to the solenoid tube blank can cause large voids in the bronze alloy, which can reduce strength. Occasionally, the bronze alloy fails to bond sufficiently to the steel solenoid tube blank. When using the TIG welding process, a great deal of heat is applied to solenoid tube blank which can cause warping and affect the shape and performance of the final solenoid actuator.